Meth also destroys parts of your brain. People lose their souls, truly. My sister was an addict for about 6 years. She didn't have the scabs but she lost alot of weight and looked horrible. She would have sold my children's souls to the devil for another hit at that time.
It was so heartbreaking for my parents since she would stay up for days then take xanax to sleep for days at a time without even getting up to eat or anything. When she lived with them my dad would say he would try and wake her by knocking on her door and he would think she was dead on the other side and would have to break the door in. Each time she was arrested and put in jail was the only time my parents felt like they could sleep at night since they knew where she was and would be safe. She hurt so many people and escaped death so many times.
She has been clean for about two years now and is a mother. That is what did it for her. But she always tells me "I will always be in recovery" "I cannot EVER forget I am an addict."
I believe alot of addicts, my sister included, are self-medicating mental illnesses such at anxiety and/or depression.